Most fuel dispensers located at service stations or other fueling areas are set on a concrete pad with associated underground piping attaching to the dispenser from below as shown in FIG. 1. This area under the dispenser is unprotected and any spills or leaks will fall directly to the soil beneath resulting in contamination of soil and/or groundwater.
A secondary containment system is a system that collects and contains fluids that leak out of another and primary containment system. For example, a primary containment system may store and deliver hydrocarbon fuels, such as gasoline and diesel oil, at a fueling station. A secondary containment system collects and contains that same fuel if a primary tank or delivery pipe should rupture or otherwise spill the gasoline. A secondary containment system also catches fuel that spills when a fill tube runs over while a fuel storage tank is being filled, for example. While the invention is described hereinafter in connection with a hydrocarbon fuel filling station storage and delivery system, it should be understood that the invention may also be used to protect any other suitable primary containment system.
The fuel dispensers in a filling station undergo routine maintenance on a regular basis. For example, the filters in a dispenser are typically changed once per month. When a filter is changed a portion of the fuel present in the dispenser downstream of the filter may drip onto the ground beneath the dispenser, even when all precautions are taken. Over an extended period of such occurrences, there may be a potential pollution problem.
Fuel spillage can also occur when less frequent types of repair work, such as meter changes, are performed on the fuel dispensers. Therefore, fuel spillage due to this type of repair work can also pose a significant pollution problem even though it occurs on an irregular basis. Also, dispensers can develop slow leaks at gaskets or other points despite regular maintenance. Such slow leaks allow a steady trickle of fuel to drain onto the ground.
With the advent of more stringent environmental regulation, it is important to attempt to contain any fuel spillage and prevent passage of such spillage to the ground, where absorption can require removal an treatment of the contaminated ground material. Hence, it is highly desirable to provide a secondary containment system for spillage from a fuel dispenser.
A number of such systems are currently available, and they include sumps, pans, bags or other devices for use under dispensers to catch spills or drips. A common characteristic of most of these systems is that they are each prefabricated so as to have holes and closure fittings therein that are properly sized and positioned to permit the various product piping and electrical conduits associated with the particular dispenser with which it is to be used, to extend through such holes and to be liquid tight so as not to let liquids enter or escape the secondary containment system. The many different dispensers involve many different types and arrangements of product piping and electrical conduits. Thus, many different styles and types of secondary containment systems are required. Furthermore, most of these secondary containment systems require that the dispensers be placed out of service during installation, which can be an expensive proposition.
Another type of secondary system, described in U.S. Pat. No. 5,332,335, owned by the assignee of this application, uses a form in-place fabrication process to accommodate a wide variety of installations without requiring a large variety of special prefabricated parts and fittings, and without any downtime during installation. However, the thermoset resin materials for such secondary containment systems are subject to shrinkage and deformation over time, resulting in stress cracks and potential leaks of the secondary containment system.